Proper Static Sag for CRF250X
Posted January 03, 2010 - 03:43 PM
I just bought new springs for my 2006 CRF250X and checked 3 calculators before I bought the springs. I had the stock spring in before I changed it out.
Weight 175 lb without gear
Riding is Enduro / Trails mostly / occasional MX track
Racetech (based on rider weight)
Stock Rear 4.8 kg/mm
Suggested Rear 5.12 kg/mm
GnarlyMX (based on rider weight)
Stock Rear 4.8 kg/mm
Suggested Rear 5.1 kg/mm
Stock Rear 5.1 kg/mm
Suggested Rear 5.2 kg/mm
I went with a 5.1 kg/mm rear spring and just set my race sag to 101mm. My free sag was measured at 32mm. My manual and other resources say that the free sag should be 10-25mm and that anything over 25mm means that the spring is too stiff. Other resources say 20-40mm is the desired range. Which one is correct?
Should I be concerned with 32mm of free sag when the calculators tell me that 5.1 is the correct spring? Is this okay or do I have to buy another spring and change it out again? If I went to a 5.0, would it fix my free sag? Why would the calculators be off?
Posted January 03, 2010 - 07:49 PM
Posted January 03, 2010 - 08:16 PM
1) Baseline - First, I placed the bike on a stand with the wheel off the ground and measured from the axle to a point on the number plate (directly above the axle. In actuality, I set the Motion Pro Sag Scale to show zero at that point since its my baseline. My reading is 0mm.
1.5) Static Sag Check just to check where my static sag was before the race sag was set, I measured it to be 60+mm....I don't remember it exactly, but I figured I was in trouble at that point.)
2) Race Sag - Next, I took the bike off of the stand stood directly on the footpegs with full gear and measured the race sag...it was off the scale (too high). I cranked on the nut little by little and set the race sag to 101mm with a friend reading the measurement off of the scale. I had to get on the bike several times and make several adjustments before I got it to exactly 101mm. I verified the measurement every time buy bouncing on the bike and getting at least 2 measurements.
3) Static Sag - I then got off the bike and measured the number plate mark with the bike on the ground with no rider....the reading was 32mm. (I bounced it several times to and took another measurement to check it).
I'm pretty sure I'm doing it right...can you verify that? So you think that my results are fishy? I thought so too....which I guess is why I'm here.
Posted January 04, 2010 - 08:21 AM
also if working with a new spring it may change after a few rides
the 1", 4" thing is just a ballpark, you may want to adjust some either way to get the bike to turn the way you like. a 1/4 " either way isn't going to change the suspension action
Posted January 04, 2010 - 09:05 PM
If I compress the spring and let it up gently, I get 42mm. If I pull the spring up and let it slowly settle down, I get 32mm. I guess, I'm even worse then...about 37mm average. I don't have any of the compression clickers moved at all from the time that I removed the springs...I'm not sure if that makes any difference though since we're worried about the spring. I really want to understand what's going on and why the calculator is off. Is there anything from the above test method that I might be doing wrong?
Posted January 04, 2010 - 09:24 PM
I'm 84kgs, no gear,and get similar specs to you with my stock rear spring - all measured properly with a helper.
What have you noticed when riding the bike with the stiffer rear compared to stock ?
Posted January 05, 2010 - 11:05 AM
I looked back at my old readings and I was at 100 race and 30 static sag with the stock spring...same as this spring??..although that spring was for 160 lb rider which I am not. (I can't verify those measurements because I might have done something wrong back then). In hindsight, I should have measured it again before I removed the stock spring. I don't know how the stock spring can be too stiff? None of this makes sense to me right now. Hopefully someone out there can help.
Posted January 05, 2010 - 05:23 PM
Posted January 05, 2010 - 09:25 PM
I think I'm just going to stick with the 5.1 and see how it goes....its too bad I can't understand this a little better....but I will keep on reading. I'm an engineer and it drives me nuts not to understand this. Thanks for the help.
By the way, my front springs were changed out with the rear spring...from 0.42 to 0.44 kg/mm....so its all balanced out
Posted January 06, 2010 - 06:00 PM
Only reason i mentioned it is it can effect your starting measurement.
One thing you might notice right off with the change to .44's in front is the fork will ride a bit higher slowing the steering. Stock I felt the bike to steer very neutral, when "I" did springs (.45 and 5.3), right off I noticed it steered slow, so I left the sag and slid the forks up a bit. Something to think about anyway.
FWIW, I'm 190 and thought the stock susp and clicker setup worked pretty good for a reasonable pace in the woods. With some groups I ride with i would have just left it. But I pretty much do everything from enduro to harescramble pace with this bike so I went ahead and sprung it for such. I think the valving is great and haven't touched it, just oil changes.
Posted January 06, 2010 - 06:18 PM
Interesting stuff about the top out of the shock. I'll have to check it out this weekend when I check through everything one last time. It would be interesting to see how much of a difference that makes.
In addition to the 0.44's, I did already move the forks up about 2.5mm in the triple clamp...so maybe I won't notice as much in regards to turning issues. Crazy though that the fork springs would make that much difference in turning. This is going to be interesting to ride again and see the difference.
I've read too that the stock X valving is pretty good...I doubt if I'll ever touch that either.
One more question...what sag do you run? Everyone seems to have a different opinion on this. I was thinking about going down to 98 or so...just curious what you recommend. I've pulled the clicker settings off a few websites...so I think I'm good to go there.